97 lines
3.8 KiB
Bash
Executable File
97 lines
3.8 KiB
Bash
Executable File
#!/usr/bin/env bash
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# Refresh the SD card as a manual boot-fallback clone of the running root
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# filesystem. Run manually after a push:
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# sudo ./failover/sync-sd-backup.sh
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#
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# R5C layout: the primary root is the eMMC (mmcblk1p1) and the SD card
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# (root UUID below) is the backup. U-Boot has no persistent env and always
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# prefers the SD if it finds a boot.scr there, so the SD's boot.scr is kept
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# renamed to /boot/boot-failesafe-rename-to:boot.scr. U-Boot then skips the
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# SD and boots the eMMC. To boot the SD: rename it back to boot.scr (e.g.
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# from another machine with the SD mounted, or from a U-Boot console).
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#
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# Not copied verbatim, so the clone keeps its own identity:
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# /etc/fstab, /boot/armbianEnv.txt copied with the root UUID rewritten
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# /boot/boot.scr never created; the eMMC's copy is
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# refreshed under the failsafe name
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# /etc/machine-id, /var/log left alone (see repo memory
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# "sd-fallback-fstab-clobber")
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# The bootloader in the SD's first sectors (idbloader/u-boot) is not touched.
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set -euo pipefail
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# Backup settings come from the host config (see hosts/vanlink.conf.example).
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# shellcheck disable=SC1090
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. "${VANLINK_CONF:-/etc/vanlink.conf}"
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: "${SD_BACKUP_UUID:?set SD_BACKUP_UUID in /etc/vanlink.conf}"
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[ "$(id -u)" -eq 0 ] || { echo "Run as root (sudo)." >&2; exit 1; }
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SD_UUID=$SD_BACKUP_UUID
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SD_ROOT_PART=/dev/disk/by-uuid/$SD_UUID
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MOUNT_POINT=/mnt/sd-backup-root
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FAILSAFE='boot-failesafe-rename-to:boot.scr'
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[ -e "$SD_ROOT_PART" ] || { echo "SD card (UUID $SD_UUID) not present." >&2; exit 1; }
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root_src=$(findmnt -no SOURCE /)
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if [ "$(readlink -f "$SD_ROOT_PART")" = "$root_src" ]; then
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echo "Currently booted from the SD card ($root_src) — refusing to sync SD onto itself." >&2
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exit 1
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fi
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root_uuid=$(findmnt -no UUID /)
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mkdir -p "$MOUNT_POINT"
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mounted_here=0
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if ! mountpoint -q "$MOUNT_POINT"; then
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mount "$SD_ROOT_PART" "$MOUNT_POINT"
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mounted_here=1
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else
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mount -o remount,rw "$MOUNT_POINT"
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fi
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cleanup() {
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if [ "$mounted_here" -eq 1 ]; then
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umount "$MOUNT_POINT"
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fi
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}
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trap cleanup EXIT
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# rsync exit 24 ("partial transfer due to vanished source files") is expected on a
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# live root — files like container shm sockets or in-progress logs routinely disappear
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# mid-sync. Tolerate that one code; anything else is a real failure and still aborts.
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# Excluded paths are also protected from --delete (no --delete-excluded), which is
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# what keeps the SD's failsafe-renamed boot script in place.
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rc=0
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rsync -aHAXx --numeric-ids --delete \
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--info=progress2 \
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--exclude=/proc/* --exclude=/sys/* --exclude=/dev/* --exclude=/run/* \
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--exclude=/tmp/* --exclude=/mnt/* --exclude=/media/* --exclude=/lost+found \
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--exclude=/swapfile \
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--exclude=/etc/fstab --exclude=/etc/machine-id --exclude=/var/log/* \
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--exclude=/boot/armbianEnv.txt --exclude=/boot/boot.scr --exclude="/boot/$FAILSAFE" \
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--stats / "$MOUNT_POINT/" || rc=$?
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if [ "$rc" -ne 0 ] && [ "$rc" -ne 24 ]; then
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echo "rsync failed (exit $rc)." >&2
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exit "$rc"
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fi
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if [ "$rc" -eq 24 ]; then
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echo "Note: some files vanished mid-sync (rsync exit 24) — normal on a live root." >&2
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fi
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# fstab and armbianEnv.txt: take the source's content, point root at the SD.
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for f in etc/fstab boot/armbianEnv.txt; do
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sed "s/$root_uuid/$SD_UUID/g" "/$f" > "$MOUNT_POINT/$f.new"
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chmod --reference="/$f" "$MOUNT_POINT/$f.new"
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mv "$MOUNT_POINT/$f.new" "$MOUNT_POINT/$f"
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done
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# Keep the SD's boot script current but dormant, so U-Boot never boots the SD
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# while the eMMC is healthy.
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install -m 0644 /boot/boot.scr "$MOUNT_POINT/boot/$FAILSAFE"
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if [ -e "$MOUNT_POINT/boot/boot.scr" ]; then
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echo "WARNING: $MOUNT_POINT/boot/boot.scr exists — U-Boot will boot the SD, not the eMMC." >&2
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fi
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echo "SD backup ($SD_ROOT_PART) synced from $root_src."
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